Invasive weeds pose a serious and increasing threat to New Mexico’s environment and economy. These weeds are tough competitors and can spread rapidly, creating large stands that can persist for many years in the environment and cause many negative impacts to our ecosystems. While these impacts are species-specific,weeds have been documented to cause the following: displacement of native plants and animals,increased fire danger, increased soil erosion, increased flood severity, increased soil salinity, and decreased water quality. In agricultural and rangeland settings, these weeds can cause severe economic impacts by decreasing crop yields and lowering available forage for range animals, resulting in a decrease in livestock health.

This booklet focuses on helping land managers, farmers, homeowners, recreationists, and others identify troublesome weeds found in New Mexico because early detection is critical to effective weed management. Forty-five plant species are included in this booklet with brief descriptions, photographs, information on what areas they invade, where they are currently located in New Mexico, and some general information on management. We urge readers to consult other resources and local experts to help in determining the most appropriate management methods for their areas. Early detection and rapid response to new infestations can save many dollars and help maintain the health, diversity, and functionality of our ecosystems.

New Mexico Noxious Weed List

Updated April 2009

The following weeds have been selected by the New Mexico Department of Agriculture to be targeted as noxious weeds for control or eradication pursuant to the Noxious Weed Management Act of 1998. This list does not include every plant species with the potential to negatively affect the state’s environment or economy.

Class A

Class A species are currently not present in New Mexico, or have limited distribution. Preventing new infestations of these species and eradicating existing infestations are the highest priorities.

Commom name

Scientific name

Alfombrilla

Drymaria arenariodes

Black henbane

Hyoscyamus niger

Camelthorn

Alhagi maurorum

Canada thistle

Cirsium arvense

Dalmation toadflax

Linaria dalmatica

Diffuse knapweed

Centaurea diffusa

Dyer’s woad

Isatis tinctoria

Eurasian watermilfoil

Myriophyllum spicatum

Giant salvinia

Salvinia molesta

Hoary cress

Cardaria spp.

Hydrilla

Hydrilla verticillata

Leafy spurge

Euphorbia esula

Oxeye daisy

Leucanthemum vulgare

Parrotfeather

Myriophyllum aquaticum

Purple loosestrife

Lythrum salicaria

Purple starthistle

Centaurea calcitrapa

Ravennagrass

Saccharum ravennae

Scotch thistle

Onopordum acanthium

Spotted knapweed

Centaurea biebersteinii

Yellow toadflax

Linaria vulgaris

Class B

Class B species are limited to portions of the state. In areas with severe infestations, management should be designed to contain the infestation and stop any further spread.

Common name

Scientific name

African rue

Peganum harmala

Chicory

Cichorium intybus

Common teasel

Dipsacus fullonum

Halogeton

Halogeton glomeratus

Malta starthistle

Centaurea melitensis

Musk thistle

Carduus nutans

Perennial pepperweed

Lepidium latifolium

Poison hemlock

Conium maculatum

Russian knapweed

Acroptilon repens

Tree of heaven

Ailanthus altissima

Class C

Class C species are widespread in the state. Management decisions for these species should be determined at the local level, based on feasibility of control and level of infestation.

Common name

Scientific name

Bull thistle

Cirsium vulgare

Cheatgrass

Bromus tectorum

Jointed goatgrass

Aegilops cylindrica

Russian olive

Elaeagnus angustifolia

Saltcedar

Tamarix spp.

Siberian elm

Ulmus pumila

Watch List

Watch List species are of concern in the state and have the potential to become problematic. More data are needed to determine if these species should be listed. When these species are encountered, please document their location and contact appropriate authorities.

Common name

Scientific name

Crimson fountaingrass

Pennisetum setaceum

Giant cane

Arundo donax

Meadow knapweed

Centaurea pratensis

Pampasgrass

Cortaderia selloana

Quackgrass

Elytrigia repens

Sahara mustard

Brassica tournefortii

Spiny cocklebur

Xanthium spinosum

Wall rocket

Diplotaxis tenuifolia

Table of Contents

Listed by flower color. The flower colors listed are the most common color for each plant. Colors may vary in the field.

AcknowledgmentThe authors wish to thank Richard D. Lee, Mark Renz, Esther E. Marquez, Ana Henke, and Susan B. Portillo for their invaluable contributions to the current and past editions of this booklet.

Black henbane / Hyoscyamus niger

Class A
Black henbane / Hyoscyamus niger

Annual or biennial that infests disturbed, open areas such as fields, roadsides, and waste areas; grows best in sandy, well drained soils. All parts of the plant are toxic to humans and livestock if ingested, and it is often described as having a foul odor.

Also Known As: Cassilata, henbell, insane root, Jupiter’s bean

Stems/Leaves: Stems (1-3 ft tall) have some branching and are densely covered with long hairs; leaves (2-8 in. long, up to 6 in. wide) alternate, gray-green, oblong or lanceolate, densely covered with sticky hairs, with toothed or lobed margins

Flowers: Five fused petals (0.8-1.2 in. long) are yellow-green in color with conspicuous purple veins and a purple throat; seeds found in green, oblong pods (0.5-1.2 in. long) that are covered with long hairs, with an opening at one end that resembles a five-pointed crown

Bull thistle / Cirsium vulgare

Class C
Bull thistle / Cirsium vulgare

Biennial (perennial under some conditions) that infests disturbed areas such as ditches, roadsides, streams, and fences.

Also Known As: Bur thistle, common thistle, spear thistle

Stems/Leaves: Several to many branches (1-6 ft tall); stems and shoots have broad, prickly wings and some fine hairs; leaves (3-12 in. long) are dark green, lobed or toothed, often hairy, with spines (0.2-0.6 in. long) along the margins; stem leaves are more lobed and spiny than basal leaves

Camelthorn / Alhagi maurorum

Class A
Camelthorn / Alhagi maurorum

Herbaceous perennial that infests a wide range of areas, particularly semi-arid areas along rivers and floodplains where plant communities are degraded, as well as disturbed areas such as roadsides, ditches, and fields.

Class B
Common teaselDipsacus fullonum

Stems/Leaves: Flowering stems (up to 6 ft) develop during the second season and branch near the upper portion; stems with several angled rows of downward prickles; basal rosette leaves are oblanceolate and usually die early in the second season; stem leaves are sessile with lanceolate shape and opposite arrangements; all leaves have short, stiff prickles on the lower midvein

Flowers: Flower heads (1.25-4 in. long) with dense white to purple flowers that bloom in a circular pattern around the ovoid to cylindrical heads; bracts at the base of the heads are prickly and generally longer than the heads; individual flowers (0.4-0.6 in. long) have spine-like bractlets

Flowers: Single flower head (0.5 in. long, 0.2 in. wide) at end of each branch with white flowers (sometimes rose to light purple); below flowers are several straw-colored bracts each with comb-like edges and a spiny tip

Eurasian watermilfoilMyriophyllum spicatum

Class A
Eurasian watermilfoilMyriophyllum spicatum

Aquatic perennial that infests riparian areas such as lakes, ponds, rivers, streams, and irrigation ditches; usually found in still or slow-moving water, but occasionally in fast-moving streams or rivers.

Purple loosestrifeLythrum salicaria

Class A
Purple loosestrifeLythrum salicaria

Perennial found in wetlands along rivers, streams, lakes, ponds, floodplains, reservoirs and ditches, as well as in some disturbed areas.

Also Known As: Bouquet violet, purple lythrum

Stems/Leaves: Multiple branched stems (1-6 ft tall) are green to purple or brown, 4-5 sided, often covered with small hairs; plants may form a clump or bush; leaves (2-6 in. long) are narrow or lanceolate with smooth margins, attach directly to stem in opposite or whorled arrangement

Flowers: Flower heads (up to 2 in. diameter) are round or hemispherical, covered with numerous green to purple or straw-colored, overlapping, spiny bracts (0.2 in. long or less), often with wooly hairs; flowers are white to purple

Spotted knapweedCentaurea biebersteinii

Class A
Spotted knapweedCentaurea biebersteinii

Herbaceous biennial to short-lived perennial that tolerates a wide range of conditions, but mostly infests disturbed areas such as roadsides, ditches, open fields, semi-arid deserts, rangelands, and grasslands.

Flowers: Single flower head (0.4-0.5 in. long, 0.3-0.5 in. wide) at end of each branch; flowers usually pinkish-purple, sometimes light purple to white; below flowers are green bracts, each with a dark brown to black comb-like tip

Leafy spurge / Euphorbia esula

Class A
Leafy spurge / Euphorbia esula

Herbaceous perennial that is adapted to many soil types and habitats; typically invades disturbed and undisturbed areas such as pastures, rangelands, abandoned croplands, roadsides, wetlands, woodlands, floodplains, riparian areas, mountain ridges, and prairies; its milky sap may cause skin and eye irritation in humans and be toxic to cattle if ingested in large quantities.

Yellow starthistleCentaurea solstitialis

Class A
Yellow starthistleCentaurea solstitialis

Annual (occasionally biennial) that infests disturbed areas such as roadsides and open fields, as well as rangelands, grasslands, open woodlands, pastures, and crop fields. Yellow starthistle is toxic to horses if consumed.

Also Known As: Golden starthistle, yellow cockspur, St. Barnaby’s thistle

Cheatgrass / Bromus tectorum

Class C
Cheatgrass / Bromus tectorum

Annual grass that infests disturbed areas such as roadsides, open fields, and ditches, as well as crop fields, rangelands, grasslands, and desert areas.

Also Known As: Downy or drooping brome, military grass, June grass, bronco grass

Stems/Leaves: Narrow stems (1-24 in. long) often droop; leaves (several inches long, 0.05-0.25 in. wide) are green to purple with closed sheaths that extend at least halfway down the stem, with some long hairs on sheaths and leaf base

Flowers: Multiple, slightly flattened grass spikes (2.5-8.5 in. long) are found at the ends of thin stems and often droop; each spike has 4-8 seeds (0.3-0.5 in. long) and each seed is tipped with a stiff bristle (0.3-0.7 in. long); spikes and seeds are green to purple or red in color

Halogeton / Halogeton glomeratus

Class B
Halogeton / Halogeton glomeratus

Annual that infests open, disturbed areas such as roadsides, open fields, and especially arid or semi-arid areas; is adapted to soils with high alkaline or salt content. All parts of the plant are toxic to livestock if ingested, especially sheep.

Hoary cress / Cardaria spp.

Class A
Hoary cress / Cardaria spp.

Perennial that infests moist areas such as irrigated pastures, rangelands, hay fields, and other crop fields; also infests disturbed sites such as roadsides, railways, and ditches. Three species occur in New Mexico: lens-podded hoary cress (C. chalapensis), heart-podded hoary cress (C. draba), and globe-podded hoary cress (C. pubescens); heart-podded is most common. Some botanists place these plants in the genus Lepidium with the same species names (L. chalapensis, L. draba, L. pubescens).

Flowers: Inflorescences are cylindrical spikes and disperse as units until maturity, but eventually break apart into joints (spikelets) over time; spikelets are cylindrical and consist of 2-5 florets, the lower 2 are fertile, and the uppermost florets are sterile

ParrotfeatherMyriophyllum aquaticum

Class A
ParrotfeatherMyriophyllum aquaticum

Aquatic perennial that infests riparian areas such as lakes, ponds, rivers, streams, and irrigation ditches; usually found in still or slow-moving water, but occasionally in fast-moving streams or rivers.

Also Known As: Brazilian watermilfoil, thread-of-life

Stems/Leaves: Emersed stems (up to 15 ft long, 0.2 in. diameter) may be branched, gray-green to reddish; leaves (0.5-1.5 in. long) 5-6 whorled, pinnate-divided with 10-15 pairs of opposite or alternate lobes (up to 0.3 in. long); lobes are linear and the main leaf axis is broader than the lobes

Poison hemlockConium maculatum

Class B
Poison hemlockConium maculatum

Biennial (sometimes annual or short-lived perennial) that typically infests open fields, pastures, ditches, riparian areas, and crop fields. All parts of the plant are extremely toxic to humans and livestock.

Stems/Leaves: Stems (up to 10 ft tall) are hollow except at the nodes, ribbed, often with purple or reddish spotting or streaking, but sometimes without streaking; leaves (4-12 in. long) are triangular, glabrous, and pinnate-divided with toothed leaflets

Flowers: Several inflorescences grow in small bunches with a single axis; flowers are very small and white

RavennagrassSaccharum ravennae

Class A
RavennagrassSaccharum ravennae

Perennial that infests the margins of riparian zones, marshes, and ditches.

Also Known As: Ravenna grass, hardy pampasgrass, plume grass

Stems/Leaves: Very tall, erect ornamental grass that forms clumps (9-13 ft tall, 4-6 ft wide); flowering stems are up to 13 ft tall, with leaves distributed on the flowering stems up to the base of the inflorescence; leaves are densely covered with long, fuzzy, brown hairs at the base that hide the ligules and the upper surface of the blade base

Flowers: Small, inconspicuous flowers grow in drooping clusters, lack petals, and are greenish in color with many small stalks that each bear a single flower; seed pods (0.5 in. in diameter) are thin, papery, green to brown, round or oval with a deep notch at the tip

Roots: Deep and extensive root system

Reproduction: From root crown or from seed; most reproduction and spread occurs through seed

Tree of heaven / Ailanthus altissima

Class B
Tree of heaven / Ailanthus altissima

Deciduous tree that can tolerate shade, pollution, and harsh soil conditions; typically infests disturbed areas such as roadsides, ditches, and waste areas, as well as natural sites such as riparian areas and woodlands.

Also Known As: Ailanthus, copal tree, varnish tree

Stems/Leaves: Erect tree with a single trunk (up to 65 ft tall); small trees have smooth, gray-brown bark while larger trees have rough bark with diamond shaped fissures; pinnate-divided leaves (1-3 ft long) have 10-22 pairs of opposite leaflets and one terminal leaflet; leaflets (3-5 in. long) are lanceolate with mostly smooth margins except for 2-4 rounded teeth at the base, often with small, circular glands on undersides of leaflets; leaves have a skunky odor when crushed

Flowers: Develop in bunches 4-8 in. long; flowers are small, greenish-yellow to white with five petals; seed pods (1-2 in. long, 0.5 in. wide) are flat, constrict around a single seed, straw-colored to reddish-brown, and grow in bunches

Roots: Taproot with shallow, creeping perennial
lateral roots

Reproduction: Root crown, lateral roots, and seed reproduction

Management Do’s and Don’ts

Maintenance of a healthy plant community and prevention are the best management methods

Physical removal is effective only if root crown and creeping lateral roots are removed

Flowers: Male and female flowers develop in separate heads on the leaf axils of the same plant; male flower heads are small, green, and develop in clusters; female flower heads develop on the leaf axils below the male flower heads singly or in small clusters; spiny female flower heads consist of 2 flowers that lack corollas and become hardened prickly burs that enclose 2 seeds at maturity

Roots: Taproot often branched

Reproduction: Seed

Management Do’s and Don’ts

Manual removal is effective, especially before burs develop

DO NOT cut and leave the plants with immature burs on the site because they can still develop viable seed

This material was produced by New Mexico State University’s College of Agricultural, Consumer and Environmental Sciences–Cooperative Extension Service in cooperation with New Mexico Department of Agriculture, Bureau of Land Management, U.S. Forest Service, New Mexico Vegetation Management Association, USDA-APHIS-PPQ, New Mexico State Highway and Transportation Department.

New Mexico State University is an equal opportunity/affirmative action employer and educator. NMSU and the U.S. Department of Agriculture cooperating.